Many different types of valves are used to control fluid flow of both gases and liquids. Commonly used types include stop cocks, plug valves, butterfly valves, gate valves, globe valves and ball valves. However, ball valves, because of their simplicity and effectiveness, make up about 35% of all fluid control valves in use. Of these ball valves, most are two-piece types, with a few heavy duty applications being one- and three-piece types. The subject matter of the current invention relates to two-piece type ball valves. A two-piece ball valve includes a body, with a ball therein having an integrated handle for rotating the ball within the body. A passage extends entirely through the ball and allows fluid flow when the ball is rotated so that the passage is aligned with the direction of flow through a pipe. When the ball valve passage is so positioned as to allow fluid flow, the ball valve handle is normally also aligned with the pipe. Conversely, when the ball valve is closed to flow, the handle is normally at right angles to the pipe.
It is often advantageous to provide power controls for ball valves in lieu of manual control via the ball valve handle. Power controls are typically useful where: (a) multiple valves must be operated in a system; (b) remote control is desired; (c) flow pressures make manual operation difficult; or (d) a combination of the aforementioned factors is present. Depending upon the application involved, it may be desirable for the ball valve to be (1) normally in the open position, and actuatable to the closed position; or (2) to be normally closed and actuatable to the open position. Power controls are typically actuated either by electric or pneumatic motors, or operators. The present invention relates to pneumatic operators.
Various types of pneumatic operators have been used to control ball valves. All such controls as are known, however, have involved the use of some form of rack and pinion arrangement connected to the ball valve, and driven by a pneumatic cylinder having a piston connected to the rack portion of the rack and pinion arrangement. Typically, such a valve operator dispenses with the usual ball valve handle, and instead provides a ball valve shaft which is rotated directly by the movement pinion gears.
While rack and pinion operators generally perform their function well, there are several disadvantages connected with their use. Most apparent of these disadvantages is the loss of mechanical advantage with the rack and pinion approach. This results from doing away with the ball valve handle, which normally would act as a lever in opening and closing the valve. The forces required to open and close a ball valve depend upon the differential pressure across the valve, as well as upon the size of the ball involved. In a typical situation involving 200 psi pipe pressure with a 1" ball valve, approximately 50 to 100 psi pneumatic pressure would be required to operate a rack and pinion valve control system. The valve control using this relatively high pneumatic pressure is necessarily more complex and more expensive than would be a valve control using a lower pneumatic pressure.
In addition, rack and pinion valve control operators are necessarily designed to work exclusively with one particular ball valve and no other. This lack of adaptability can be a significant restraint on the users of the valve controls, especially where multiple valves are involved, as is often the case. Further, rack and pinion ball valve controls are typically designed to operate valves only from one particular starting orientation, for example from a normally open position. If a normally closed position were later desired, additional parts might be required to effect the change in set-up, or such a set-up change might even be found to be impossible. A further, related limitation of the rack and pinion approach is that the set-up must adopt precisely a particular orientation of the pneumatic cylinder and shaft relative to the ball valve. Any variation from the required orientation will generally result in the rack and pinion arrangement not working properly. This inflexibility of set-up requirements may at times be inconvenient due to the complex and unpredictable nature of piping arrangements that may occur. Finally, rack and pinion operators are somewhat complex in their design, and therefore tend to be expensive.
It is therefore an object of the present invention to provide a ball-valve control operator which is simple and efficient in design and thus is relatively inexpensive.
It is a further object of this invention to provide an operator which has a significantly improved mechanical advantage, and is therefor capable of utilizing less pneumatic pressure to perform its function, resulting in greater simplicity of operation and significantly reduced cost.
It is still a further object of this invention to provide a valve control which is adaptable for use with a variety of ball valves and pipes.
Finally, it is an object of this invention to provide a ball valve control operator which may be mounted in a variety of ways depending upon the needs of the fluid flow system involved. In particular, it is desired to provide an operator which may be set up to accommodate a valve which is in either a normally open or a normally closed position.